FR2978006A1 - Section of fluid transport pipe for e.g. land transportation of hydrocarbons, has electrical heating system that comprises connecting units to perform electrical connection and linking together electric wires of each of groups - Google Patents

Abstract

The section (1) of pipe comprises a casing (3) in which the fluid to be transported flows. An electrical heating system comprises electric wires (4) arranged around casing and intended to be powered, through connection elements (21,22) to connect electric wires joined together. The wires are powered by electric supply. The wires are arranged in set (9) of groups (10a-10c) where each is intended to be supplied by distinct phase. The heating system comprises connecting units (7) to perform connection and linking together electric wires of each of groups. Independent claims are included for the following: (1) fluid transport pipe; and (2) laying method for hydrogen transport pipe.

Description

The technical sector of the present invention is that of heating systems for fluid transport conduits. The invention particularly relates to submarine or terrestrial transport of hydrocarbons over long lengths. For the transport of fluids in cold environments, for example for the underwater transport of hydrocarbons, a technical solution consists in heating the conduits to avoid the formation of obstructions consecutive to a cooling of the fluid. It is thus necessary to maintain a minimum temperature by heating the transport pipe. An electric heater can be used for this purpose. The robustness of the heating equipment must be adapted to the environmental conditions in which the transport pipe is placed. Underwater hydrocarbon pipelines can be installed at depths of up to several kilometers and are therefore more difficult to access for maintenance or repair operations. These same difficulties can be found for terrestrial conduct in a hostile environment. The electrical heating son of the transport conduit are generally pressed against the conduit in which the hydrocarbons circulate and arranged under a protective envelope. A thermal insulation layer disposed beneath the protective envelope is generally provided around the electrical heating wires and around the conduit in which the hydrocarbons circulate, in order to promote the exchange of heat with the inner conduit and to limit losses to outside. A double-jacketed duct, also referred to as a "pipe-in-pipe", comprises an outer protective metal casing arranged around an inner metal casing which forms the internal duct in which the hydrocarbons circulate.

Once installed, the pipes for the transport of hydrocarbons can measure several tens of kilometers. The electric heating cables therefore also have similar lengths of several tens of kilometers. The electrical son arranged along the transport conduit can in particular be connected in series, thus constituting a line running along the pipe. Three lines powered by a three-phase power supply are for example connected to one end of the conduit to the three phases of the power supply and are connected to each other at the other end of the conduit, to form a balanced electrical star arrangement. Each of the three lines generally consists of a plurality of electrical cables connected in series and interconnected by electrical connectors. For example, several sets of three lines are arranged along the transport duct and over its entire periphery, each constituting a heating circuit. This is Joule heating, but this would also apply if the heater had a magnetic component (inductive heating). A problem is however that in case of faulty connection between two son, a complete line becomes inoperative and therefore the heating circuit which it is also part. The heating of the transport conduit is then degraded despite the fact that electrical safety components can disable the lines associated with the defective line.

This problem concerning faults in the electrical connections can arise for any type of sections assembled end to end to form a conduit. For straight sections that are typically 12 meters, 24 meters or 72 meters long, and assembled at sea on a barge assembly, to form the conduit as and when required, this problem is all the more important that we can no longer intervene on the pipe after its installation in the seabed. It is also known that the failures of the electrical systems are mainly related to failures occurring at the level of the connections. The multiplication of wires and sections to achieve a long pipe thus leads to systems that may have several tens of thousands of connections, which can bring the overall risk to an unacceptable level. For example, for a 100 km pipe laid in 20m sections, with 60 wires, it is necessary to make 3000 connections per km, or 300,000 connections in all. It thus appears a need, for conduits heated by electric wires, to improve the robustness of the electric heating system vis-à-vis the defects in the electrical connections.

The present invention aims to overcome one or more of the disadvantages of the prior art by providing an electrical heating system of a section for which the robustness is improved vis-à-vis the defects in the electrical connections.

This objective is achieved by means of an electric heating system of at least one section of a conduit for transporting a fluid, the conduit comprising an envelope in which the fluid to be transported circulates, the heating system comprising electrical wires arranged around the casing and intended to be supplied with energy, via connection elements, by a power supply comprising a plurality of phases, characterized in that the electrical wires are arranged in at least one set of several groups of several electrical wires each, each of the groups in said assembly being intended to be powered by a separate phase, the electric heating system comprising connecting members making an electrical connection and interconnecting the electrical son of each of said groups. Each set thus constitutes a heating circuit. According to another feature of the invention, said connecting members are arranged in an intermediate zone between the two ends of the section. According to another feature of the invention, the connecting elements, arranged at both ends of the section, are associated with identification elements son belonging to the same group. According to another particularity of the invention, said set comprises as many groups as the number of phases of the power supply, each group of said set comprising the same number of electric wires, the groups of said set being of the same impedance.

According to another particularity of the invention, the heating system comprises a plurality of sets of several groups of several electrical wires. According to another feature of the invention, the heating electric wires, arranged against the casing, made of metal, for conveying the fluid, are electrically insulated by an electrically insulating and thermally conductive sheath. Another object of the invention relates to a section of a fluid transport conduit comprising a first envelope in which the fluid to be transported circulates, characterized in that it is equipped with a heating system according to the invention. . According to another feature of the invention, the section comprises a second envelope arranged around and at a distance from the first envelope, forming an annular housing space of the connection members and the group or groups of electrical son. According to another feature of the invention, certain sections arranged along the pipe comprise an annular reinforcement connecting the first and second casings and forming an annular wall between the first and second casings, annular wall in which are arranged passages receiving the organs connection to connect together the wires of the same group. Such reinforcement is in particular designated by "bulkhead". According to another particularity of the invention the annular reinforcement equipped with its connecting members constitutes a watertight partition, pneumatically isolating the downstream annular of the upstream annular.

According to another feature of the invention, the annular reinforcements are arranged at regular intervals along the pipe, for example every km. According to another feature of the invention, the section comprises an external sign indicating the presence of said connecting members. Another object of the present invention relates to a fluid transport duct comprising sections equipped with electric heating wires interconnected by said connection elements at the junction between the sections, said connecting elements arranged at one end of the duct. being connected to said power supply or to a neutral point of a final electrical connection, characterized in that it comprises one or more sections according to the invention. Such a conduit is for example a submarine hydrocarbon transport conduit. The final electrical connection is for example a neutral point of a star connection for a three-phase power supply. According to another particularity of the invention, the conduit comprises sections not equipped with said connection members electrically connecting the electrical wires of the same group to each other, the two types of sections being equipped with the same number of connected electrical heating wires. in series at the junction between two sections. According to another particularity of the invention, the power supply, of the three-phase power supply type, comprises its three phases connected to one end of the conduit and to the electrical wires, all the electrical wires of all the groups of all the assemblies being furthermore connected. between them at the other end of the duct to form a star electrical assembly, for each heating circuit. According to another characteristic of the invention, each heating circuit comprises protection devices (for example fuses) and control elements, arranged at an electrical supply panel, outside the conduit. Other characteristics, advantages and details of the invention will be better understood on reading the additional description which will follow of embodiments given by way of example in relation to drawings in which: FIG. section according to the invention; FIG. 2 represents a conduit according to the invention; FIG. 3 represents an electric heating system for a duct according to the invention; FIG. 4 represents an annular reinforcement; - Figure 5 shows a sectional view of a housing in the annular reinforcement, wherein is installed a connection member according to the invention; - Figure 6 shows an exploded view of a connection member according to the invention providing the electrical connection 10 of three son together; - Figures 7 and 8 show the end-to-end of two ends of two sections; - Figure 9 shows two sections joined together before the connection of their outer casing; FIG. 10 represents the establishment of two half-junction tubes of the outer casings of two double-jacketed sections; Figure 11 shows the matching of the connecting elements, organized in groups, with respect to each other; - Figure 12 shows the measurement of impedance between two son depending on whether they belong to the same group or to different groups. The invention will now be more fully described. FIG. 1 shows a section 1 intended to be assembled with other sections to form a conduit 2 for transporting a fluid, such as hydrocarbons. The section 1 comprises a first envelope 3, or inner envelope, in which circulates the fluid to be transported. A second envelope 11 is disposed around and away from the first envelope 3. The two envelopes 3 and 11 define an annular space 26. This annular space 26 receives for example the heating system and a thermal insulation of the first envelope 3. The first envelope 3 may be metallic as is the second envelope. The first and second envelopes are for example made of steel or another metal. The second casing 11 has been shown in transparency so as to show the heating system, no insulating material being shown in particular in FIG. 1. It would also be possible to provide a single jacket duct and electric heating wires clad to the outside. the metal casing by a holding means such as straps or a plastic envelope. The heating system comprises electrical wires 4 arranged around the first casing 3. These wires will be supplied with energy, via connection elements 21 and 22, using a multi-phase power supply. By the phases of the power supply, we will designate the supply points supplied by this one. A neutral wire may also be designated as one of the phases of the power supply. Those skilled in the art will recognize that a DC power supply can also be considered and that the discussion is based on the notion of phase for clarity of presentation. The electrical son 4 are arranged in a set 9 of several groups 10a, 10b and 10c of several electrical son 4 each. Each group in this set 9 will be powered by a separate phase. The electric heating system further comprises connecting members 7 making an electrical connection and interconnecting the electrical son 4 of each of these groups 10a, 10b and 10c.

As can be seen in FIG. 1, the annular space 26 of the double-jacketed section is used to house a part of the heating system, including members 7 for connecting the electrical wires 4 of each group. An external indicator sign 15 is made and indicates the presence of the connecting members 7 connecting the son of a group between them. This indicator sign 15 is made to be visible outside the section 1. The sign 15 is for example painted or etched outside the outer envelope 11.

The connecting elements at one end 8a are for example female connectors 22 and the connecting elements at the other end 8b are male connectors 21. Thus the sections joined together by welding at their fluid transport envelope 3 are associated with electric cables 4 electrically connected one after the other. In particular, a double-walled conduit makes it possible to protect the heating and thermal insulation system. The connecting members 7 are for example arranged in an intermediate zone between the two ends 8a and 8b of the section 1, as shown in FIG. 1, but the connecting members 7 could also be arranged at the level of the connecting elements 21 and 22. Figure 2 shows a conduit 2 according to the invention. Its heating system comprises a set 9 comprising three groups 10a, 10b and 10c of three son 4 each. Each group is powered by a separate phase. Terminals 29a, 29b and 29c disposed outside the outer casing 11, are each connected to a group 10a, 10b or 10c at one end of the duct 17. These terminals 29a, 29b and 29c are connected by elsewhere each at a phase 6a, 6b and 6c of the power supply 5.

The duct 2 extends between a fluid emitter assembly 28 (for example a wellhead) and a receiver assembly 27 (for example a water oil separation unit). The duct 2 shown in FIG. 2 comprises sections 1 equipped with members 7 for connecting the wires of the same group. These sections 1 are marked in particular by an outer sign which corresponds for example to an annular reinforcement 12 integrated in the section 1, but other types of signs could be provided and arranged at any location of the section. A section equipped with connecting members 7 and equipped with a marker may be inserted regularly as the duct 2 is made. The duct 2 comprises, for example, also sections 16 that are not equipped with members 7. connecting the electrical wires 4 electrically between them, the two types of sections being equipped with the same number of electrical wires 4 for heating, these son 4 being connected in pairs, in series, at the junction 25 between two sections 16 or 1. An electric neutral point 24, also called star point, is made at the end of the duct. For very long lengths can be provided several power points distributed along the pipe. It will also be possible to have a power supply 5 of the three-phase power supply type whose three phases 6a, 6b and 6c of the power supply are connected firstly to one end 17 of the conduit 2, to the electrical wires 4. On the other hand, At the other end 18 of the duct 2, all the electrical wires 4 of all the groups 10a, 10b and 10c of all the assemblies 9 are moreover electrically connected to one another to form a neutral point 24 of an electrical star arrangement. Figure 3 shows a heating system of a conduit for transporting a fluid. The connections between the son of successive sections are schematized by two points arranged vis-à-vis. The power supply 5 here delivers three phases 6a, 6b and 6c of a balanced three-phase power supply. Thus one can connect the phases together at the end 18 opposite the end 17 to which the power supply is connected, to form a star balanced arrangement.

The heating system comprises several sets 9 of several groups 10a, 10b, 10c of several electrical wires 4. Only two sets 9 have been shown for the sake of convenience, but more could be provided. The control and protection connection elements which would be inserted between the generator 5 and the heating circuits 9 are not represented. Each set 9 comprises as many groups 10a, 10b and 10c as the number of phases 6a, 6b and 6c of the supply 5. Each set 9 here comprises three groups. Each group 10a, 10b or 10c of each set 9 comprises the same number of electrical wires 4, the groups 10a, 10b or 10c of each set 9 thus having the same impedance. In the circuit diagram of FIG. 3, sections 16 not equipped with connecting members 7 are associated with sections 1 equipped with these connection members 7. It would also be possible to provide a duct, each of the sections of which is equipped with connecting members 7 according to the invention, but advantageously the connecting members 7 are associated with an annular reinforcement 13 regularly spaced apart and spaced a distance from each other. approximately 1 km in order to limit the relative displacements between inner and outer envelope due to the thermal transient phases. This distance may be shorter in the vicinity of bends associated with changes of direction. Advantageously, if a connection between connecting elements 21 and 22, at the junction 25 between two sections, is defective, the current in the son concerned is cut only until the next connection member 7, either side of this faulty connection. The portion of unpowered son being of short length compared to the total length of a line extending along the conduit 2, the impedance of the group of son is very little modified and thus retains a balanced and functional assembly. The connection member 7 makes it possible to guarantee a supply of all the downstream wires in the group of this member 7. The supply is in fact supplied by at least one of the wires of the group upstream, to the member 7 connection. The electric heating wires 4, arranged against the casing 3 made of metal, are wires 4 electrically insulated by a sheath. This sheath is electrically insulating and thermally conductive and allows the release of heat by Joule effect. The electrical wires are for example made of copper and the electrical insulation made of PVC, silicone or a fluorinated polymer. The sections assembled end to end are for example straight sections. Such sections typically measure 12 m, 24 m or 72 m. One could also provide to equip a wound section, typically a length of 1 km, several connecting members 7 according to the invention, arranged regularly along the wound section. Thus the heating system according to the invention makes it possible to overcome faulty electrical connections, like other electrical failures such as a break in an electrical wire 4. The heating remains operational for all the heating wires and all around. of the duct, by providing a determined heating power. It would also have been possible to provide groups each consisting of two son or four son or five son or more son.

The number of sets of groups of threads and the number of threads in the groups of the same set will, for example, be chosen as a function of the total number of threads with which the section is equipped in order to produce groups of similar impedance. The number of groups can be a multiple of the number of phases. Figure 4 shows an annular reinforcement 12 which is intended to mechanically connect the inner and outer shells 3 and 11 Such an annular reinforcement 12 is also referred to in English as "bulkhead". This reinforcement 12 advantageously separates a section into two half-sections which are welded on each side of this reinforcement 12, but it could also be installed at the end of a section. The reinforcement comprises an inner ring 30 and an outer ring 31 joined together by an annular wall 13. Passages 14 are arranged in this wall 13. When making a duct, the inner casings of one section are first welded on both sides of the inner ring. The outer shells of a section are then welded on either side of the outer ring 31. Thus a section 1 equipped with the annular reinforcement 12 is formed. The outer ring 31 is visible outside the section, which allows to constitute a marker 15, as described above. Figure 5 shows a sectional view taken at a passage 14 equipped with a connecting member 7. The connecting member 7 may be arranged in the passage 14. On the other hand, the gap between the upper ring 31 and the lower ring 30 corresponds to the height of the annular space 26, in which the wires 4 electric are arranged. Unoccupied passages 14 may possibly be used to carry out a continuous communication all along the annular 26 of the duct. FIG. 6 shows an example of connecting member 7 interconnecting three electrical wires 4. The member 7 comprises a cylindrical central portion 32 of dimensions adapted to be maintained in the previously described passage 14 made in the annular reinforcement 12.

The portion 32 makes it possible to close the annular reinforcement in a sealed manner, thus making the annular spaces upstream and downstream independent. This tight closure limits the consequences of the intrusion of a fluid in the ring.

The medial portion 32 is extended by three male plugs 33 on either side of the central portion 32. These six plugs 33 are all electrically interconnected. The outside of the portion 32 and the plugs 33 is electrically insulated, only the ends of the plugs being conductive. Female sockets 34 disposed at the end of electrical wires 4 are positioned on the plugs 33 to make an electrical connection. The connection of the three son 4 of a group is thus performed. Advantageously, this electrical connection can be made internally to the section, the electrical connections then being more reliable than that performed at sea when joining sections for laying a conduit. The electrical junction of the son of the same group, made internally to the section, also allows to test this connection soon after the manufacture of the section. We thus gain in reliability. FIG. 7 shows the junction of two sections 1a and 1b of a double-wall duct. Each section comprises its outer casing 11 surrounding a layer of insulating material 19 disposed on electric heating wires 4 themselves arranged against an inner casing 3. The ends of the wires 4 are equipped with a connector 21 or 22. A male connector 21 of the section la will for example be connected to a female connector 22 of the other section lb. The connectors 21 and 22 are each each equipped with an identification element 20. FIG. 8 shows the two ends of the inner shells 3 interconnected by a weld made at the junction of the two inner shells. The electrical wires 4 are connected to each other. Thus the electric current can be transmitted from one section to another. The electrical wires 4 are thus connected two by two by a connecting element in the form of the male connector 21 or the female connector 22. FIG. 9 shows the coverage of the electrical wires, at the junction, by an insulating material Thermal 19. The insulating material 19 is thus arranged all along the duct, around the inner casing. Figure 10 shows the installation of two half-cylinders 23 which will make the junction between the two outer casings 11. Thus a continuous outer casing is made all along the duct double jacket. Here the inner envelope of a section is of greater length than its outer envelope. One could also provide a section whose outer casing is the same length as the inner casing, the outer casing is then translated to clear the place where the junction 25 of the inner casings is made. After the electrical connections have been made and the insulation has been laid, the outer casing can be translated to be joined, by welding, to the outer casing of the other section. Note that in the case of assembly of sections of about 24 meters, comprising 60 son, assembled end to end to form a 2 km conduit, the number of electrical connections to the junction of the sections is about 5000. On then understands all the better the importance of mitigating the consequences of possible electrical connection faults. Figure 11 shows the positioning of the connecting elements 21 and 22 relative to each other. The connecting elements 21 and 22, arranged at both ends of the section, are associated with identification elements of the son 4 belonging to the same group. In the case of sets 9 each comprising three groups 10a, 10b and 10c, each of the groups comprising three son, the same element indicating group membership will be repeated three times, then another element 20 will be repeated three times and and so on. Two successive groups are thus associated with distinct indicator elements.

The element 20 indicating membership of the same group may be arranged on a facet of the connecting element 21 or 22. An indicator element 20 belonging to the same group is for example made by a painted pattern or embossed .

In Figure 11, there is shown in a non-limiting manner, on the male and female connectors, different identification patterns such as triangles, stars, squares or circles. Colors could also be used.

Advantageously, this allows to identify the son of the same group. Figure 11 shows an example of connections made in accordance with the indications provided by the different identification elements. In this example each group is composed of the same number of threads, whatever the set to which it belongs. Thus we can connect one group with another, this on the condition of connecting all the son of the same group to the son of another group. The identification elements 20 advantageously make it possible not to connect two distinct groups to each other. The connectors can also be mechanically linked in groups, thus making it possible to connect all the wires of one group to another group by a single movement. This reduces the number of operations and maintains the continuity of each group throughout the course. One could also provide, as shown in Figure 12 to electrically test the lines to determine which belong to the same group. Such an electrical test is for example an impedance measurement. The impedance, measured by the Ohmmeter M1, between two wires of the same group is thus smaller than the impedance, measured by the Ohmmeter M2, between two wires belonging to different groups, except when performing the conduct between the star point and the first connection 7. It should be obvious to those skilled in the art that the present invention allows other variants. Therefore, the present embodiments should be considered as illustrating the invention defined by the appended claims.

Claims (14)

REVENDICATIONS1. Electric heating system of at least one section (1, la, lb) of a conduit (2) for conveying a fluid, the conduit comprising an envelope (3) in which the fluid to be transported circulates, the system of heating comprising electric wires (4) arranged around the casing (3) and intended to be supplied with energy, via connection elements (21, 22), by an electric power supply (5) comprising a plurality of phases (6a, 6b , 6c), characterized in that the electrical wires (4) are arranged in at least one set (9) of several groups (10a, 10b, 10c) of several electric wires (4) each, each of the groups in said set being to be supplied by a separate phase (6a, 6b, 6c), the electric heating system comprising connecting members (7) making an electrical connection and interconnecting the electrical wires (4) of each of said groups. 2. Electric heating system according to claim 1, characterized in that said connecting members (7) are arranged in an intermediate zone between the two ends (8a, 8b) of the section. 3. heating system according to claim 1 or 2, characterized in that the connecting elements (21, 22), arranged at both ends (8a, 8b) of the section, are associated with elements (20) for identifying the son (4) belonging to the same group. 4. Heating system according to one of the preceding claims, characterized in that said assembly (9) comprises as many groups (10a, 10b, 10c) as the number of phases (6a, 6b, 6c) of the supply ( 5), each group (10a, 10b, 10c) of said assembly (9) comprising the same number of electrical wires (4), the groups (10a, 10b, 10c) of said assembly (9) being likewise impedance. 5. Heating system according to one of claims 1 to 4, characterized in that it comprises a plurality of sets (9) of several groups (10a, 10b, 10c) of several electrical son (4). 6. Heating system according to one of claims 1 to 5, characterized in that the electric heating son (4), arranged against the casing (3) made of metal, fluid transport, are electrically insulated by a sheath electrically insulating and thermally conductive. 7. Section (1, la, lb) of a conduit (2) for transporting a fluid comprising a first envelope (3) in which the fluid to be transported circulates, characterized in that it is equipped with a system heating system according to one of claims 1 to 6. 8. Section according to claim 7, characterized in that it comprises a second casing (11) disposed around and at a distance from the first casing (3), forming an annular space for housing the connecting members (7) and the sets (9) of groups (10a, 10b, 10c) of electrical wires (4). 9. Section according to claim 8, characterized in that it comprises an annular reinforcement (12) connecting the first and second envelopes (3, 11) and forming an annular wall (13) between the first and second envelopes (3, 11). ), annular wall (13) in which are arranged passages (14) receiving said connecting members (7). 10. Section according to one of claims 7 to 9, characterized in that it is a straight section (1, la, lb). 11. Section according to one of claims 7 to 10, characterized in that it comprises an indicator outer sign (15) of the presence of said connecting members (7). 12. conduit (2) for conveying a fluid comprising sections equipped with heating wires (4) interconnected by said connecting elements (21, 22) at the junction (8a, 8b) between the sections, connecting elements disposed at one end (17, 18) of the duct being connected to said electrical supply (5) or to a neutral point (24) of a final electrical connection, characterized in that it comprises one or more sections ( 1, la, lb) according to one of claims 6 to 10. 13. Conduit (2) according to claim 12, characterized in that it comprises sections (16) not equipped with said connecting member (7) electrically connecting the electrical son (4) between them, the two types of sections being equipped with same number of electrical wires (4) connected in series to the junction (25) between two sections (16, 1, la, lb). 14. Conduit according to claim 12 or 13, characterized in that the power supply (5), of the three-phase power supply type, comprises three phases (6a, 6b, 6c) connected to one end (17) of the conduit (2), to the electric wires (4), all the electrical wires (4) of all the groups (10a, 10b, 10c) of each assembly (9) being furthermore connected to each other at the other end (18) of the conduit (2) for forming a star electrical assembly (24).